Assessment of sex hormone-binding globulin and osteocalcin in patients undergoing coronary artery bypass graft surgery

Objective:To determine sex hormone-binding globulin (SHBG) and osteocalcin (OC) levels in patients undergoing coronary artery bypass graft surgery to clarify the status of peripheral thyroid metabolism and to correlate SHBG a nd OC with thyroid hormones and adverse postoperative events. Design: Prospective study. Setting: University medical center. Participants: Fifty randomly selected patients undergoing coronary artery b ypass graft surgery. Interventions: On the morning of surgery before induction of anesthesia; 30 minutes after cross-clamping of the aorta; 2 hours and 6 hours after aorti c cross-clamp removal; and on the first, second, third, and seventh postope rative mornings, blood samples were drawn and analyzed for OC, SHBG, triiod othyronine (tT3). free T-3 (fT(3)), thyroxine (tT(4)). free T-4 (fT(4)). th yroid-stimulating hormone, and thyroid-binding globulin. Adverse postoperat ive events were recorded. Measurements and Main Results: Mean tT3 and fT(3) decreased on average by 3 5% and 18% but remained within the normal range perioperatively. Similarly, mean SHBG and OC remained within the normal range. More than half of the p atients investigated (60%) had OC concentrations below the normal range. Pa tients with pathologically decreased tT(3) (n = 6) and tT(4) (n = 16) intra operatively and postoperatively had SHBG and OC concentrations similar to t hose in patients with normal tT3 and tT(4) levels. Patients with postoperat ive complications had significantly lower OC levels preoperatively and on t he first postoperative morning than those with an uneventful postoperative recovery. Conclusion: Despite significant intraoperative and postoperative decreases in levels of thyroid hormones, low T3 syndrome was rare in this patient pop ulation. Unchanged concentrations of SHBG and OC in patients with pathologi cally decreased tT(3) or tT(4) suggest normal local thyroid exposure at the tissue sites in these patients. OC may act as a predictor for postoperativ e outcome. Copyright (C) 2000 by WB. Saunders Company.